Method of combatting the obstruction of gas circulation in gas drilling



Sept. 15, 1964 DR. HOLBERT ETAL 3,148,729

- METHOD OF COMBATTING THE DESTRUCTION OF GAS CIRCULATION IN GASDRILLING 2 SheetsSheet 1 Filed July 1, 1959 A TTORNE Y5 Sept. 15, 1964D. R. HOLBERT ETAL 3,148,729

METHOD OF COMBATTING THE OBSTRUCTION 0F GAS CIRCULATION IN GAS DRILLING2 Sheets-Sheet 2 Filed July 1, 1959 pm R. IWM

RMO Paw/ BY WQwMMWfiJ ATTORNEYS United States Patent 3,148,729 li/ETHGD@F CGMBATTTNG THE GBSTRUCTEQN 0F GAS CIRCULATHON 1N GAS DRILLTNG Don R.Heibert and Robert 6. Perry, Tulsa, Okla, assignors, by niesneassignments, to Sinclair Research, Inc

New York, N.Y., a corporation of Delaware Filed July 1, 1959, Ser. No.824,263 Claims. (Cl. 166-5) This invention relates to improvements in amethod using gas as a circulation medium in the drilling of wells. It isparticularly concerned With a method for expeditiously and economicallycombatting the effect of a reduction or cessation of gas circulationwhen gas drilling wells through permeable formations, i.e. thosecontaining gas, liquid or loosely consolidated strata. A method of thistype is described in copending application Serial No. 686,198 filedSeptember 25, 1957, now Patent No. 3,011,547, hereby incorporated byreference.

As described in that application, when an obstruction of aircirculation, i.e. a reduction or cessation thereof, is experiencedduring an air drilling operation and the obstruction is attributed tothe ingress of gas, liquid or loosely consolidated earth particles intothe bore from an adjacent stratum, resin-forming material is introducedinto the well bore. This material is of the type that will harden attemperatures encountered in the well bore, which in many cases arebetween about 50 to 200 F. The quantity of resin-forming material usedmust be adequate to extend horizontally into the formation of ingressfor a distance sufiicient to securely seal this formation subsequent tothe hardening of the resinous material to prevent further ingress ofunwanted extraneous materials. This distance usually extends at leastabout six inches into the formation. Moreover, in this method it isimperative that the resin-forming material occupy the well bore adjacentthe formation of ingress when the hardened resin is formed. Accordingly,after the introduction of the resin-forming material into the well bore,detection means are employed to track the upper level of theresin-forming material; gas or liquid, e.g. air or water pressure, isapplied to bring this upper level approximately adjaccnt the upper levelof the strata of ingress, and the resinous material is maintained inthis position until it solidifies. Following solidification of theresinous material, air drilling is resumed.

In the practice of the method described in the abovementionedapplication, the resinous material is introduced into the well bore,forming a column above the upper level of the permeable formation, thedrill pipe is raised and the resinous material is displaced downwardlyin the well bore and into the formation to seal the portion of theformation exposed in the well bore. Frequently, when following thisprocedure formations exhibiting high areas of permeability, e.g.crevices, are encountered, for instance crevices ltifi and 1%1 as shownin the drawings. These crevices, in addition to consuming largequantities of expensive resinous material, prolong the sealingoperation. For instance, during the sealing operation considerablequantities of expensive resinous material are consumed in the creviceslocated above the permeable formation to be sealed and particularly thecrevices located in the formation to be sealed due to the pressureapplied on the resinous material column extending above the upper levelof the permeable formation. During the displacement operationsignificant quantities of resinous material can be lost unfortunately,into either of these types of crevices. In connection with the creviceslocated in the formation, as pressure is applied to the upper level ofthe resinous material, greater quantities of this material are displacedinto the upper portions of the formation as the material is generallydisplaced into "Ice the upper levels and progressively down to the lowerlevels of the formation. The resin displaced in and sealing theformation takes the form of an inverted pyramid as shown in the drawingsof the cited application. If the permeable formation to be pluggedcontains a crevice, large quantities of resinous material can be lost inthe crevice before the lower portion of the formation is sealed whenthis procedure is followed. Thus this results in an inefficient use ofthe expensive resinous material. Additionally, as the resinous materialis usually precatalyzed with polymerization catalyst prior to itsintroduction into the well bore, sufiicient quantities of the resinousmaterial must be available to insure proper sealing of the exposedformation. Accordingly, when formations exhibiting high areas ofpermeability are encountered, the amount of resinous material needed isestimated empirically with a bogey run in which an inexpensive solution,e.g. sugar-water solution, is substituted for the expensive resinousmaterial. The data provided by such a run include an estimation of thequantities of resinous material required to seal the exposed formationas well as an estimation of the time required for displacing theresinous material into the formation. The time required for thedisplacement operation is useful in determining the amount of catalystnecessary to provide ample working time before polymerization of theresinous material causes a change from a mobile liquid to a solid mass.

An object of the present invention is the provision of a method forexpeditiously combatting the effect of a reduction or cessation of gascirculation when gas drilling Wells through permeable formations.Another object of the present invention is the provision of a method forthe efficient employment of resinous material in a method forexpeditiously combatting the effect of a reduction or cessation of gascirculation when gas drilling wells through permeable formations. Theseobjects are accomplished when using the method of the present inventionwhich is designed to obviate the use of a bogey run and provide forsimultaneous injection of the resinous material over the entire portionof the permeable formation exposed in the well bore with the use of astring of tubing.

According to the method of the present invention, when an obstruction ofair circulation, i.e. a reduction or cessation thereof, is experiencedduring an air drilling operation and the obstruction is attributed tothe ingress of gas, liquid or loosely consolidated earth particles,particularly salt water, into the bore from an adjacent stratum,resin-forming material is introduced into a string of tubing, forinstance the drill string, extending downwardly below the permeableformation. The resinous material is conducted downwardly in the tubing.A first portion of the resinous material is conducted through the lowerextremity of the tubing and forms a column in the annular space betweenthe tubing and the wall of the well bore which column at least coversthe formation to be sealed. The level of this annular column ismaintained while the upper level of the remaining or secondary portionof the resinous material in the tubing is pressured to force permeableformation sealing amounts of resinous material into the permeableformation. The resinous material is maintained in this position until itsubstantially solidifies. The solid resin is drilled through anddrilling is continued with gas circulation to remove cuttings from theWell.

The method of this invention can best be described with reference to aspecific example and the drawing, FIG- URES 1 through 10, in whichseveral distinct phases of the method are illustrated.

Referring to the drawing, FIGURE 1, the numeral 10 represents the earthssurface through which a well bore 12 is being drilled to anoil-producing formation with rotary drill pipe 14 containing a rotarybit 16 at the lower end. Pressurized air is introduced into drill pipe14 at the surface of the earth, is conducted downwardly therein, exitsthrough opening 15 of rotary drill bit 16 at the site or formation ofdrilling 18, and passes upwardly through annulus 20, surrounding drillpipe 14, carrying relatively small as well as larger rock particles fromthe site of drilling to the earths surface.

In FIGURE 2 rotary drill bit 16 passes through crevice we, andpenetrates a salt Water formation 22 at its upper level 24 as indicatedby a reduction in air circulation as well as the muddy nature of theparticles recovered from the site of drilling. The depth of the drillbit is noted and thus the position of upper level 24 of salt waterformation 22 is known. In FIGURE 3 drilling is continued through thesalt water-bearing formation contain ng crevice 101, air circulationeventually ceases due to the back pressure of the salt water, a columnof salt water 28 rises in the well bore and drill pipe to level 30 inannulus 29 and upper level 31 in drill pipe 14, the lower level 26 ofsalt water formation 22 is penetrated by rotary drill bit 16 anddrilling is discontinued. Occasionally, in cases Where the waterformation is of considerable depth, it may not be possible to penetratethe lower level of the formation before water production stops furtherdrilling.

A small amount, e.g. gallons, of radioactive fluid, e.g. aqueous iodine131 solution, is injected into drill pipe 14 and is shown at position42. A detecting device 32 consisting essentially of a Geiger-counter isinserted to locate the radioactive fluid.

In FIGURE 4 gas pressure is applied to the liquid column in drill pipe14 to move the upper level 44 of the column of radioactive liquid 42downwardly in the drill pipe to the position shown. As the column movesdownwardly salt water exits through openings of rotary drill bit 16 andforms annular salt water column 4-8 with an upper level 59 in theannular space formed between the drill pipe and the walls of the wellbore. An amount of resinous material at least sufiicient to cover theportions of formation 22 exposed to well bore 12, for instance, fiftygallons of resinous material, weighted, e.g. with CaCl to be heavierthan the salt water in the well bore, consisting essentially of 20weight percent of a mixture of 5% N,N'-methylene-bis-acrylamide and 95%acrylamide in water along with 0.3 weight percent of ammonium persulfateand 0.6 weight percent of nitrilo-tris-prd pionamide is injected downdrill pipe 14 at a rate of 2 gallons per minute and positioned intubular area 36 located above upper level 44 of the radioactive liquid.Detecting device 32 is used to locate the position of radioactive liquid42. A second radioactive isotope layer 43,. e.g. of iodine 131, is addedon top of the resinous material which thus has a leading radioactiveedge 42 and a rear radioactive edge 43.

In FIGURE 5 pressurized air is introduced downwardly in drill pipe 14and moves the resinous material, preceded by radioactive material 42,through opening 15 and up the annulus formed between the drill pipe andthe well bore walls to form an annular column of resinous material 52(with an upper level 54) covering the portions of salt water formation22 exposed in the well bore. In this operation the pressure on theresinous material is insuiiicient to force a significant quantity intothe adjacent formation and the resinous material displaces annular saltwater column 48 upwardly to new level Stl. As the annular resinousmaterial column 52 is moved upwardly, radioactive material 42 islocated, thus upper level 54, with device 32 which is located withindrill pipe 14, to insure upward movement of upper level 54 of theresinous material at least adjacent and preferably a short distancebeyond the upper level 24 of salt water formation 22. By noting thedepth of the device 32 the position of upper level 54 is known. Annulus20 is sealed at the surface with casing head 21 and air pressure up tothe limit of the surface casing is used to maintain upper level 54 ofan- 4. nular column of resinous material 52 in the position shown.Detecting device 32 is raised (not shown) to locate layer 43 thus upperlevel 56 of the secondary column (tubular) of resinous material 58.

In FIGURE 6 pressurized air (250 p.s.i.) is introduced downwardly indrill pipe 14 and forces resinous material through opening 15 and causesthe simultaneous injection of resinous material in area 62 into theentire portion of permeable formation 22 exposed in the Well bore asshown by the indicating arrows. During this phase layer 43 thus upperlevel 56 of resinous material tubular column 58 is tracked with device32.

In FIGURE 7 the displacement of resinous material by air is discontinuedwhen the upper level 56 of resinous material tubular column 58 isapproximately even with upper level 54 of annular resinous materialcolumn 52 as determined by observing the depth of tracking device 32 anddiscontinuing the displacement when the device 32 reaches the depthpriorily noted for upper level 54. In FIGURE 8 the drill pipe and bitare lifted as shown. The well is shut in and the resinous materialsmaintained in this position by regulating the air pressure in both theannulus and drill pipe until the resinous material commences topolymerize. However, the drill pipe can be raised above the resinousmaterial before polymerization time and solidification of the resin asshown in FIGURE 9. The resinous material is copolymerized to asemi-solid gel in about minutes although copolymerization time can becontrolled by changing the concentration of the catalyst or by addingsmall amounts of potassium ferricyanide to delay polymerization. InFIGURE 10, following the solidification of the resinous material, airpressure is discontinued, detection device 32 is removed, the salt wateris blown out, air circulation down drill pipe 14 to rotary drill bit 16is initiated, drilling is resumed, the solidified resinous material isdrilled through, and the drilling continues downwardly into the earthssurface while removing cuttings from the well bore by air circulationdown the drill pipe and up the well annulus.

The above example illustrates a method designed to remove gascirculation obstructions in a rotary drilling method employing a gas asthe circulating medium. The advantages in using this method are readilyapparent to those skilled in the art and include, for instance economyand speed. Both of these advantages result in the manner in which thismethod is conducted, for example, since (a) removal of the drill pipeand bit from the well bore is not mandatory, (b) a resinous material isused that will copolymerize at ambient conditions in the well bore, (0)the polymerization time of the resinous material is controllable, (d)detection means are employed in a manner to place the resinous materialproperly in the well bore to permit excellent air circulation whendrilling is resumed, (e) a bogey run is not required and (f) theexpensive resinous material is eliiciently employed, since loss of theresinous material in crevices, for instance crevices and 101, can beavoided or minimized. Although this invention is illustrated with a mostexpedient and economical method, it will be obvious to those versed inthe art to use various modifications incorporating the essentialfeatures of this method such as the removal of the drill pipe and bitfrom the well bore complctely and using packers to block fluid flow upannulus 25! during the displacement of the resin from within the tubingand into the well bore.

The resin-forming material employed in the method of the presentinvention is catalyzed before placement in the bore and is of the typethat will harden at temperatures encountered in the well bore, which inmany cases are between about 50 to 80 or 200 F. The quantity ofresin-forming material used must be adequate to extend horizontally intothe formation of ingress for a distance sufficient to securely seal thisformation subsequent to the hardening of the resinous material toprevent further ingress of unwanted extraneous materials. This distanceusually extends at least about six inches into the formation. Moreover,in this method it is imperative that the resin-forming material occupythe well bore adjacent the formation of ingress when the hardened resinis formed.

Accordingly, after the introduction of the resin-forming material, whichhas a specific gravity higher than the ingressing well fluid, into theWell bore tubing, detection means are employed to track the upper levelof the annular column of resin-forming material; and gas or liquid, e.g.air or water pressure, is applied to maintain this upper levelapproximately adjacent the upper level of the strata of ingress. Gas orliquid is also applied to the upper level of the secondary portion ofresinous ma terial in the tubing to force permeable formation sealingamounts of this material into the permeable formation. The resinousmaterial is maintained in this position until it solidifies. Althoughgas or liquid pressure can be em ployed in this method, gas ispreferable to liquid since (a) it permits better control of the resinousmaterial and (b) the well bore hole is drier following thepolymerization of the resin-forming materials and no time must be spentdrying the hole before drilling. The gas pressure will depend upon thenature of the obstruction encountered and the depth of the permeableformation and is generally greater than about 150 psi. but is usuallyabout 150 to 1000 psi. Since tremendous pressures can be required, itmay be desirable to produce such pressures by employing liquid and gasin combination, e.g. provide a liquid coloumn above the resin-formingmaterial and exert air pressure on the liquid column. Followingsolidification of the resinous material, air-drilling is resumed.

In the practice of this method, it may be desirable to place in thetubing 21 small volume of liquid or primary buffer before theresin-forming material to prevent contact of the resinous material withthe materials in the lower portion of the well bore, e.g. salt Water andgenerally radioactive material to facilitate tracking the upper level ofthe annular column of resinous material. This primary buffer should havea density in between that of the well bore fluid and the resinousmaterial so that the bufier will have a tendency to float or remainbetween the Well fluid and resinous material. Examples of suitablebuffers are radioactive fluids, e.g. iodine 131 solution in mixtures of60% by volume of kerosene and 40% by volume of carbon tetrachloride witha specific gravity heavier than the Well fluid and lighter than theresinous material or mixtures of 82% by volume of kerosene and 18% byvolume of tetrabromoethylene.

It may also be desirable to place on the resin-forming material a volumeof liquid or secondary buffer possessing radioactive characteristicsappreciably different from that, if any, of the resin-forming materialto facilitate tracking of the resin-forming material; the density of thesecondary buffer should be less than that of the resinous material andpreferably greater than that of any fluid, liquid, or gas, used topressure the resinous material to its position of hardening. Suitablesecondary buffers are radioactive fluids, e.g. iodine 131, in 2% byweight of calcium chloride in water with specific gravity lower than theresinous material.

The detection means employed for tracking the position of the upperlevel of the annular column of resinous material in the well bore asWell as the upper level of the secondary portion of the resinousmaterial (tubular column) in the tubing can vary as long at it candetect the upper level of the resinous material in the Well annulus. Inone method, a soluble radioactive tracer, e.g. iodine 131, may beinjected into the polymerizable material and a Geiger-counter attachedto a line can be employed to locate the upper levels of the annular andtubular columns of polymerizable material and thus by checking the depthof the Geiger-counter, these positions of the polymerizable material areknown. In the preferred 6 method primary and secondary radioactivebuffers are employed as described in the above example.

Among the resin-forming materials which are utilized are those affordingmodified polyester-type resins, and U.S. Patents Nos. 2,255,313;2,443,735 and 2,443,741 give examples of these materials. The first ofthese patents describes resin-forming materials containing a resin whichis a substantially linear polyhydric alcohol ester of an unsaturatedpolybasic acid material of the maleic type mixed with a liquidsubstituted-ethylene body of resin-forming characteristics which iscopolymerizable and miscible with the resinous material, for instance avinyl compound. Thus the resin or plastic obtained from this mixture canbe the reaction product of a maleictype polybasic acid, a polyhydricalcohol and a vinyl compound. This patent lists a number of suitablereactants; for instance, the polybasic acid may be maleic anhydride,maleic acid, fumaric acid, etc. and the preferred acid materials containa single double bond and up to about 5 carbon atoms. The polyhydricalcohols are preferably dihydric of the type which react with dibasicacids to yield linear molecules or linear polyesters. Various of thedihydric alcohols are listed in the patent, for instance diethyleneglycol, ethylene glycol, triethylene glycol, propylene glycol, etc., andthe preferred alcohols are the glycol and glycol ethers of up to about12 carbon atoms. In the resin-forming material the polyester resinformed from the dibasic acid and the glycol is mixed with an ethylenicpolymerizable body, preferably a vinyl compound such as vinyl esters,vinyl ethers, styrene, etc. The mixtures containing the polyester resinand ethylenic compound, for instance styrene, are sold commercially anda catalyst and a promoting material can be added to provide acomposition which will be satisfactory as the resin-forming material inthis invention.

US. Patent No. 2,443,735 described a resin-forming material whichincludes a resin possessing a plurality of polymerizable reactive alpha,beta enal groups and at least one material containing the CH =C linkage.The resin component of this mixture is produced by the esterification ofan alpha, beta unsaturated polycarboxylic acid with a polyhydricalcohol, such as a glycol, while the CH =C body can be, for instance,styrene. Thus, the ingredients of this resin-forming material can begenerally the same as those described with reference to US. Patent No.2,255,313. In Patent No. 2,443,741 similar resin-forming materials aredisclosed. However, the CH =C body is of the polyallyl type, forinstance a polyallyl ester, and a number of these are mentioned in thispatent.

As a more specific example, a resin-forming material suitable for use isprovided by mixing generally about 8 to 35 percent and preferably about20 to 35 percent by volume of an unsaturated polyester resin of the typedisclosed in these patents as a solution containing about 30 to 60percent by volume of styrene; about to "65 percent by volume of anesterified, unsaturated polybasic acid; about 0.01 to 4 percent byvolume of a promoter; and about 0.01 to 3 percent by volume of apolymerization catalyst. The polyester resin component can be Laminac4111, a polyethylene glycol maleate resin mixed with styrene. To adjustthe specific gravity of the resinforming mixture within a desirablerange, a chemically inert densifier can be added which has a lowviscosity, for instance about 1 to -15 centipoises, preferably about 1to 5, at 60 F.; and a specific gravity of over about 1.5; and which iswater-insoluble and non-polymerizable. Among the preferred densifiersare included benzoyl chloride, dichlorobenzene and dinitrodiphenyl. Aparticularly eifective densifier is tetrabrornoethane.

In order to facilitate the polymerization reaction the addition of asmall amount of a promoter, for example about 0.01 to 4 weight percentof cobalt naphthenate or dimethyl aniline, is preferred. Apparently, thepromoter acts as a linking agent and in combination with the catalystinitiates a faster polymerization reaction at the relatively lowpolymerization temperatures encountered in a Well bore. By varying theamount of promoter and catalyst the Working life of the resin-formingmaterial can be regulated. Among the promoters which can be employed inthis invention are the organic acid salts of metals such as aluminum andcalcium, for instance calcium stearate, aluminum stearate, aluminumnaphthenate and calcium naphthenate.

The polymerization catalysts utilized to effect the copolymerization orcondensation reactions between styrene and the modified polyesterresin-styrene solution can be the organic peroxide catalysts such asbenzoyl peroxide, methylethyl ketone peroxide, tetrabutyl hydroperoxideor cyclohexanone peroxide. Particularly effective catalysts are a 60%solution of methylethyl ketone peroxide in dimethyl phthalate or benzoylperoxide in a 50% mixture with tricresyl phosphate. As mentioned theWorking life of the resin-forming material is dependent upon the amountsof polymerization catalyst and promoter present as well as thetemperature in the well bore, and generally polymerization startsimmediately after the catalyst and promoter have been added.Consequently, at ambient temperatures Within a Well bore, for instanceabout 70 to 75 F., the amount of catalyst employed preferably is in therange of about 0.4 to 0.7 percent by volume of the resin-formingmaterial which afiords a Working life of about 30 to 60 minutes. Theamount of catalyst required to sustain the working life of theresinforming material will increase as the temperature is decreased andthus at lower temperatures of about 50 to 60 F. the amount of catalystemployed may be as high as 3 percent.

Another class of desirable liquid resin-forming compositionsparticularly suitable for use in the method of the present inventioninclude an aqueous solution of an alltylidene bisacrylamide, anethylenic comonomer, and calcium chloride, the bisacrylamide having theformula:

in which R' II is a hydrocarbon residue of an aldehyde and R is a memberof the group consisting of hydrogen and a methyl radical.

The other comonomer is a solid, liquid or gaseous ethylenic (i.e.contains at least C=C radical) compound with a solubility of at leastabout 2 by weight, and preferably at least about in Water and whichcopoly'merizes with the aforesaid bisacrylamide in an aqueous system.Although not essential in practicing the invention, it is preferred toselect an ethylenic comonomer which is preferably soluble or at leastself-dispersible in water with appropriate stirring, as such, forexample, methylenebisacrylamide, which is capable of polymerizing.

In addition to the comonomer N,N-methylene bisacrylamide set out in theexamples hereinafter, any of the alkylidene bisacrylamides correspondingto the above formula which are described and claimed in Lundberg PatentNo. 2,474,846 hereby incorporated by reference, or mixtures thereof maybe used as cross-linking agents. Only slight solubility is required ofthe alkylidene bisacrylamide in view of the small amount used;therefore, this component may have a water solubility as low as about0.02% by weight at 20 C. but a solubility of at least about 0.10% ismore desirable for general purposes.

A wide variety of ethylenic cornonomers or mixtures thereof arecopolymerizable with the alkylidene bisacrylamides; those having aformula containing at least one C=C group, hereinafter referred to asthe ethenoid group, and having appreciable solubility in water aresuitable for use in the present invention. See US. Patent No. 2,801,985,hereby incorporated by reference. As set forth in this patent theunsubstituted bonds in the ethenoid group may be attached to one or moreof many different atoms or radicals including hydrogen, halogens, suchas chlorine and bromine, cyano, aryl, aralkyl, alkyl, and alkylene withor without solubilizing groups attached to these hydrocarbons. Inaddition, the substituents on the ethenoid group may comprise one ormore hydrophilic groups including formyl, methylol, polyoxyalkyleneresidues and quaternary ammonium salt radicals,

o 0i' (OH);

OOCH, -OOCCH -SO X, Where X is H, NH an alkali metal or an alkylamine;CONR and where each R is hydrogen, alkylol, lower alkyl or apolyoxyalkylene radical; and COOR and CH COOR', Where R is a H, NHalkali metal, alkaline earth metal, organic nitrogenous base, allcylol,lower alkyl or polyoxyalkylene radical. The large number of combinationsand proportions of the various suitable substituents makes itimpractical to list all compounds in this category which may beemployed. The Water solubility of these substances is known to dependchiefly on the number and type of hydrophilic and hydrophobic radicalstherein; for example, the solubility of compounds containing an alkylradical diminishes as the length of the alkyl chain increases and arylgroups tend to decrease Water solubility Whereas the aforesaidhydrophilic substituents all tend to improve the solubility of a givencompound in water. Accordingly, the comonomer should be selectedaccording to chemical practice from those containing suflicienthydrophilic radicals to balance any hydrophobic groups present in orderto obtain the requisite water solubility of monomer.

Among the water-soluble ethenoid monomers, those containing an acrylylor methacrylyl group are especially recommended. These are exemplifiedby N-methylol acrylamide, calcium acrylate, methacrylamide andacrylamide. Other suitable ethenoid compounds are acrylic acid; otherN-substituted acrylamides, such as N-methyl acrylamide, N 3hydroxypropylacrylamide, dimethylamino-propylacrylamide, N-ethylolacrylamide; acrylonitrile; saturated alkyl esters of acrylic acid, i.e.methyl acrylate, B-hydroxyethyl acrylate; ethylene glycol andpolyethylene glycol acrylates, an example being the reaction product offi-hydroxyethyl acrylate or acrylic acid with about 1 to about 50 molsor more of ethylene oxide; salts of acrylic acid, i.e. magnesiumacrylate, sodium acrylate, ammonium acrylate, zinc acrylate,{B-aminoethyl acrylate, ,B-methyl aminoethyl acrylate, guanidineacrylate and other organic nitrogenous base salts, such as diethylamineacrylate and ethanolamine acrylate; quaternary salts like alkylacrylamidopropyl dimethylamino chloride; acrolein, p-carboxyacrolein,butenoic acid; a-chloroacrylic acid; fi-chloroacrylic acid; as well asmethacrylic acid and its corresponding derivatives.

Maleic acid and its corresponding derivatives including partial esters,partial salts, and ester salts thereof; maleamic, chloromaleic, fumaric,itaconic, citraconic, vinyl sulfonic, and vinyl phosphonic acids andtheir corresponding derivatives and mixtures thereof. Derivatives ofthis kind and other suitable compounds include u,3-dichloroacrylonitrile, methacrolein, potassium methacrylate, magnesiummethacrylate, hydroxyethyl methacrylate, zinc 18- chloroacrylate,trimethylarnine methacrylate, calcium achloromethacrylate, diethylmethylene succinate, methylene succindiamide, monomethyl maleate, maleicdiamide, methylene maloanamide, diethyl methylene malonate, methylisopropenyl ketone, ethyl vinyl ketone, propyl vinyl ketone, vinylformate, vinyl lactate, vinyl acetate, vinyl bromoacetate, vinylchloroacetate, vinyl pyrrolidone, allyl levulinate, allyl alcohol,methallyl alcohol, diallyl carbonate, allyl lactate, allyl gluconate,di(,B-aminoethyl) male- :ate, di(methyl-aminoethyl) maleate,di(N,N-dimethyl B- aminoethyl) maleate, sulfonated styrene, vinylpyridine, maleic anhydride, sodium maleate, ammonium maleate, calciummaleate, monopotassium maleate, monoammoniurn maleate, monomagnesiummaleate, methyl vinyl ether, N-aminoethyl maleamide, N-aminoethylmaleimide, alkyl aminoalkyl maleamides, N-vinyl amines, N-allyl amines,heterocyclic ethenoid compounds containing nitrogen in a tertiary aminogroup, and the amine and ammonium are salts of said cyclic compounds,N-vinyl acetamide, N-vinyl- N-me'thyl formamide,N-vinyl-N-methylacetamide, N-vinyl succinimide, N-vinyl diformamide,N-vinyl diacetamide, vinyl sulfonyl chloride, vinyl sulfonic acid salts,vinyl sulfonic acid amides, vinyl oxazolidone, allyl amine, diallylamine, vinyl methyl pyridinium chloride, and allyl trimethyl ammoniumchloride to name only a few of the operative compounds.

The preferred resin-forming material which can be utilized in the methodof the present invention is in an aqueous medium and has an initialviscosity approximating that of water. This material can be formed bydissolving a mixture of acrylamide and N,N'-methylene-bis-acrylamide infresh water. Generally, this mixture contains about 1 to 25 weightpercent of N,N'-methylene-bis-acrylamide and about 99 to 75 weightpercent of acrylamide. The aqueous solution will usually include fromabout weight percent of this mixture to its limit of solubility andpreferably this amount is about 5 to 25 percent. Although the acrylamideas such is preferred, its nitrogen atom could be substituted as with ahydroxy methyl or a hydroxy ethyl group. Ammonium persulfate is anacceptable catalyst to polymerize the aqueous mixture and it can beemployed with a promoter such as sodium thiosulfate ornitrilo-tris-propionamide. The amounts of each of the catalyst andpromoter usually are about 0.1 to 2 weight percent based on the aqueoussolution of resin-forming material, and these amounts can be varied togive the desired working life. For instance, a weight ratio of catalystto promoter of l to 2 in an aqueous solution containing 20 weightpercent of the acrylamide and N,N-methylene-bis-acrylamide (95%acrylamide and 5% N,N'-methylene-bis-acrylamide) will give a workinglife at 70 F. of about 60 to 120 minutes when the catalyst plus promoteris about 0.5 to 1.5% of the aqueous solution. A specific resin-formingmaterial found useful is an aqueous solution which contains 20 weightpercent of resin-forming material (95 weight percent of acrylamide, 5weight percent of N,N'-methylene-bis-acrylamide), 0.6 weight percent ofnitrilo-tris-propionan1ide, 0.3 weight percent of ammonium persulfate,and the balance being water. The mixture has an initial viscosity (1.3centipoises) approximating that of water (which is about 0.5 to 1.5centipoises under the conditions in many well bores) and is not greaterthan about 2.0 centipoises over a working life of at least about 90minutes to facilitate its placement in the desired well area. Themixture can be made heavier than salt water by the addition, forinstance of calcium chloride or other suitable densifier. The aqueoussolution of amides can advantageously be used as the resin-formingmaterial as it has a lesser tendency to emulsify in the well than do themodified polyester-type compositions.

It is claimed:

1. A method for combatting the obstruction of gas circulation indrilling wells employing gas as the circulation medium through a drillpipe tubing with a lower opening, wherein the obstruction results fromthe ingress of extraneous materials into the well bore from asubterranean formation, the steps comprising introducing weightedresinforming material into the tubing extending downwardly in the Wellbore below the upper level of the formation of ingress, conducting aportion of the resin-forming material through the tubing to form anannular column of resin-forming material covering the formation ofingress in the annular space provided between the tubing and the portionof the formation of ingress exposed in the well bore, tracking the upperlevel of the annular column of resin-forming material in the well borewith detection means, applying pressure to maintain the upper level ofthe annular resin-forming material column at the approximate depth ofthe upper level of the formation of ingress as determined by saidtracking while applying pressure to the resin-forming material remainingin the tubing to force formation sealing amounts of resinformingmaterial into the formation of ingress exposed to the resin-formingmaterial in the well bore, maintaining the resin-forming material inthis position until it substantially polymerizes, drilling through thepolymerized resin, and continuing drilling with gas circulation toremove cuttings from the well.

2. The method of claim 1 wherein the resin-forming material containsradioactive leading and rear edges, and tracking said leading and rearedges with radioactive detection means to aid in properly positioningthe resinforming material in the well bore.

3. The method of claim 2 wherein the resin-forming material consistsessentially of acrylamide and an alkylidene bisacrylamide.

4. A method for combatting the obstruction of air circulation indrilling wells employing air as the circulation medium through a drillpipe tubing with a lower opening, wherein the obstruction results fromthe ingress of extraneous materials into the well bore from asubterranean formation, the steps comprising introducing an aqueoussolution of resin-forming material consisting essentially of acrylamideand alkylidine bisacrylamide, weighted to be heavier than the extraneousmaterial, into the tubing extending downwardly in the well bore to theapproximate depth of the lower level of the formation of ingress,conducting a portion of the resin-forming material through the openingin the tubing to form an annular column of a resin-forming materialcovering the formation of ingress in the annular space provided betweenthe tubing and the portion of the formation of ingress exposed in thewell bore, tracking the upper level of the annular column ofresin-forming material in the well bore with detection means, applyingpressure to maintain the upper level of the annular resin-formingmaterial column at the approximate depth of the upper level of theformation of ingress as determined by said tracking while applyingpressure to the resin-forming material remaining in the tubing to forceformation sealing amounts of resin-forming material into the formationof ingress exposed to the resin-forming material in the well bore,maintaining the resin-forming material in this position until itsubstantially polymerizes, drilling through the polymerized resin, andcontinuing drilling with air circulation to remove cuttings from the we5. The method of claim 4 wherein the resin-forming material containsradioactive leading and rear edges, and tracking said leading and rearedges with radioactive detection means to aid in properly positioningthe resinforming material in the well bore.

6. The method of claim 5 wherein the alkylidine bisacrylamide isN,N-alkylene-bisacrylamide.

7. The method of claim 6 wherein the resin-formingmaterial consistsessentially of about 1 to 25 weight percent ofN,N'-methylene-bisacrylamide and about 99 to 75 weight percent ofacrylamide.

8. A method for combatting the obstruction of air circulation indrilling wells employing air as the circulation medium through a drillpipe tubing with a lower opening, wherein the obstruction results fromthe ingress of extraneous materials into the well bore from asubterranean formation, the steps comprising introducing an aqueoussolution of resin-forming material consisting essentially of acrylamideand alkylidine bisacrylamide, weighted to be heavier than the extraneousmaterial, into the tubing ex\ 1 1 tending downwardly in the Well bore tothe approximate depth of the lower level of the formation of ingress,conducting a portion of the resin-forming material through the openingin the tubing to form an annular column of a resin-forming materialcovering the formation of ingress in the annular space provided betweenthe tubing and the portion of the formation of ingress exposed in thewell bore, tracking the upper level of the annular column ofresin-forming material in the well bore with detection means, applyingpressure to maintain the upper level of the annular resin-formingmaterial column at the approximate depth of the upper level of theformation of ingress as determined by said tracking while applyingpressure to the resin-forming material remaining in the tubing to forceformation sealing amounts of resin-forming material into the formationof ingress exposed to the resinforming material in the well bore,raising the drill pipe above the resin-forming material, and maintainingthe resin-forming material in this position and substantiallypolymerizing the material, drilling through the polymerized resin, andcontinuing drilling with air circulation to remove cuttings from thewell.

9. The method of claim 8 wherein the resin-forming material containsradioactive leading and rear edges, and

tracking said leading and rear edges with radioactive detection means toaid in properly positioning the resinforming material in the Well bore.

10. The method of claim 9 wherein the alkylidine bisacrylamide isN,N'-alkylene-bisacrylamide,

References ited in the file of this patent UNITED STATES PATENTS

1. A METHOD FOR COMBATTING THE OBSTRUCTION OF GAS CIRCULATION INDRILLING WELLS EMPLOYING GAS AS THE CIRCULATION MEDIUM THROUGH A DRILLPIPE TUBING WITH A LOWER OPENING, WHEREIN THE OBSTRUCTION RESULTS FROMTHE INGRESS OF EXTRANEOUS MATERIALS INTO THE WELL BORE FROM ASUBTERRANEAN FORMATION, THE STEPS COMPRISING INTRODUCING WEIGHTEDRESINFORMING MATERIAL INTO THE TUBING EXTENDING DOWNWARDLY IN THE WELLBORE BELOW THE UPPER LEVEL OF THE FORMATION OF INGRESS, CONDUCTING APORTION OF THE RESIN-FORMING MATERIAL THROUGH THE TUBING TO FORM ANANNULAR COLUMN OF RESIN-FORMING MATERIAL COVERING THE FORMATION OFINGRESS IN THE ANNULAR SPACE PROVIDED BETWEEN THE TUBING AND THE PORTIONOF THE FORMATION OF INGRESS EXPOSED IN THE WELL BORE, TRACKING THE UPPERLEVEL OF THE ANNULAR COLUMN OF